Deep ocean transponder

ABSTRACT

A lightweight underwater transducer is described in which the anchor contains a battery pack and a receiver-transmitter which are connected through an electrical cable to an upwardly directed transducer carried on a flotation housing. The flotation is supplied by means of a single thin-walled glass ball whose diameter is typically about 16 inches, but which may be larger or smaller. The flotation housing consists of a pair of flanged hemispheres which capture and protect the glass ball and to which is attached a tethering rope of a desired length to prevent buoyant load from being applied to the electrical cable. During handling and deployment, most of the length of the rope and electrical cable are taken up in a coil which is, in part, secured by a corrodible magnesium link and which is released in the sea by the breaking of the corrodible link.

United States Patent [1 1 Ewing et al.

both of Calif.

The Bendix Corporation, North Hollywood, Calif.

Filed: Aug. 14, 1972 App]. No.: 280,296

[73] Assignee:

U.S. Cl. 340/2, 9/8 R, 340/3 E Int. Cl. G015 9/66 Field of Search 340/2, 3 E, 8 S;

[56] References Cited UNITED STATES PATENTS 5/1968 Bridges. 340/2 7/1970 Ewing 340/2 Primary Exqminer -Richard A. l arley klitbrney-fiiobert C. Smith and William F Thornton Jan. 15, 1974 5 7] ABSTRACT A lightweight underwater transducer is described in which the anchor contains a battery pack and a receiver-transmitter which are connected through an electrical cable to an upwardly directed transducer carried on a flotation housing. The flotation is supplied by means of a single thin-walled glass ball whose diameter is typically about 16 inches, but which may be larger or smaller. The flotation housing consists of a pair of flanged hemispheres which capture and protect the glass ball and to which is attached a tethering rope of a desired length to prevent buoyant load from being applied to the electrical cable. During handling and deployment, most of the length of the rope and electrical cable are taken up in a coil which is, in part,

secured by a corrodible magnesium link and which is released in the sea by the breaking of the corrodible link.

5 Claims, 2 DrawingFigures PATENTEnJmsmn :3;'ras.404

SHEET 1 [IF 2 PATENTEDJAH 15 4974 3 735 494 sumanrz DEEP OCEAN TRANSPONDER BACKGROUND OF THE INVENTION Various types of deep ocean transponders have been available for many years. They are anchored at a specified location on the ocean bottom, usually in a known pattern, and used as navigation aids for ships. Upon receiving an interrogating signal, the transponder will respond with a code signal identifying itself, and this, together with similar signals from other transponders, enables those on the ship to determine its location.

Transponders presently, in use are typically very large, bulky, heavy and expensive. Since they are frequently designed to operate for periods exceeding one year without attention, they necessarily contain a substantial weight of batteries, typically of the lead-acid variety, which are housed in the anchor structure. The flotation means employed has often consisted merely of a tank of hydrocarbon liquid, such as kerosene, which is sealed to prevent leakage and to which is attached the electronic receiver-transmitter assembly and the necessary acoustic transducer. The flotation tank must, therefore, support itself plus the electronic assembly and transducer, plus the cable extending between itself and the anchor. Since the buoyancy of kerosene per unit volume is not great, such tanks tend to be relatively large and heavy to handle in air as, of course, is the anchor containing the batteries. The combination, attached by means of a cable of some considerable length, tends to be so heavy and awkward to handle on shipboard as to be somewhat dangerous to personnel.

Lighter flotation arrangementshave been devised in which a plurality of glass spheres of moderate diameter I such as inches or 12 inches are placed in a freeflooding housing of plastic material with means such as rubberized horsehair to assure that these glass spheres are prevented from being jarred against each other during handling or because of a collision with some obstacle under water. In order to provide the requisite amount of flotation from these glass balls, it has been necessary to use a substantial number of such balls, and the risk of loss of the transponder through implosions of the glass balls is very real. Should one of the balls collapse, a chain reaction of implosions frequently results, causing enough of the spheres to bedestroyed that the transducer can no longer be maintained in the desired position and attitude.

SUMMARY The transponder disclosed in the present application utilizes much the same electrical components described above, but these are housed differently and supported in the water differently from conventional practice. Glass spheres of considerably greater diameter than those previously used have recently become available, and such spheres will withstand external pressures of the order of 10,000 pounds per square inch. Spheres of approximately 16 inches in diameter afford a very substantial buoyancy such that only a single such sphere may be required. The specific underwater transponder described herein consists of an assembly including one such glass ball encased in a polyethylene housing consisting of a pair of mating hemispheres fastened together to confine the ball. Mounting means extending from the top of the polyethylene housing supports the vertically directed underwater transponder, and cabling means from the transponder extends around the housing and down to the anchor structure consisting of a battery pack encased .in a strong metal housing designed to withstand the substantial pressures referred to above. Also contained within this housing is an electronic package constituting a receiver transmitter assembly and which is powered by the battery pack.

Because of the difficulty of handling the separate anchor and flotation units which, as deployed, will be separated by many feet, the cable extending from the anchor to the transducer as well as a polypropylene tethering rope extending from eyebolts on the anchor housing to the flotation housing are coiled in such manner as to reduce the distance between the anchor and the flotation housing to approximately 18 inches. This coil is secured by simple string ties-or; tape which are removed prior to deployment and also by means of a corrodible magnesium link which ties the anchor housing, coil and flotation housing together during storage and handling. The magnesium link basically consists of a length of magnesium welding rod formed into an endless loop and includes dissimilar metal accelerators to aid in causing corrosion and/or embrittlement of this link upon exposure to sea water. When the magnesium link corrodes and breaks, the buoyant force of the glass ball in the flotation housing causes the flotation housing to move upwards away from the anchor and uncoil the polypropylene rope and electrical cable, thereby extending the transponder to its full operational height.

DESCRIPTION OF THE PREFERRED' EMBODIMENT Referring to FIG. 1, a heavy cylindrical anchor member 10 is shown with an electrical connector 12 and a cable 14 which is arranged into a coil 16 and which is then attached through further connector means 18 to an underwater transducer 20. Anchor member 10 has been shown broken away at its center since its height is normally substantially greater than its diameter. The transducer 20 is supported by the flotation housing 22 consisting of a pair of mating flanged hemispherical polypropylene housing members which are secured together by any suitable fastening means in such manner as to contain and restrain the thin-walled glass sphere 24 which may be of approximately 16 inches diameter or more. Also fastened to the flotation housing 22 are a pair of supporting links 26, 28 which cooperate with the connector means 18 to support the transducer 20 in the desired upward facing attitude. Transducer 20 includes ring-shaped piezoelectric elements which cause the transducer to operate in a squirting" mode such that as the rings are energized from. the electrical signal, they expand and contractradially thereby creating a force alongtheir axis directed upwardly. Similarly, upon interrogation, the acoustic force impinging upon the transducer 20 will cause itto be vibrated radially, thereby causing an electrical signal to be gener ated which is supplied to the receiver in housing 10.

A plurality of eyebolts 30 are positioned at the end of housing 10 nearest the flotation housing 22, and one or more similar eyebolts 32 are located at the opposite end of said housing. Eyebolts 32 are used to assist in lifting the assembly from the deck of the deploying ship into the water. A polypropylene rope 34 is formed into a sling arrangement including a pair of loops 36 which feed through openings on suitable clamp means also carried in eyebolts 30. Polypropylene rope 34 is also coiled into coil 16 along with the electrical cable 14, and both are temporarily held in the coil by means of temporary ties 40. A length of magnesium welding rod is formed into a loop 42 which is closed at its ends by means of a connector 44- which is normally of steel. Also attached to the magnesium wire length 42 are one or more steel accelerators 46 which are simply small folded steel members which contact the magnesium and cooperate with the action of the sea water to accelerate the corrosion of the magnesium link 42.

FIG. 2 shows the transponder as it would appear in deployed position. The anchor may find a position lying on its side on the bottom since its height may be several times its diameter, although it has been shown cut off for purposes of convenience in the drawing. It will be observed that this figure shows a battery pack consisting of a plurality of battery sections 48 within the housing as well as the electronic assembly 50 including the receiver-transmitter assembly which is connected to the transducer 20 through the electrical cable 14. In this figure, the corrodible link 42 has broken, releasing the coil 16 and permitting the buoyant housing assembly 22 to rise to the maximum distance permitted by the length of the polyethylene tethering rope 34. Again, for convenience in drawing, the cable 14 and the tethering rope 34 have been shown cut to indicate the much greater length that actually exists between the anchor 10 and the flotation housing 22. This distancg, as extended, will normally be from 11 to 20 feet. ()bviously, the greater the length of the tethering rope 34, the greater the possible lateral displacement that can occur between the anchor and the transducer 20 due to the action of underwater currents.

We claim:

1. An instrumentation assembly for mooring on the bottom of a body of water including a housing,

an anchor tethered to the portion of said housing normally positioned nearest said bottom,

a sonar transducer fastened to said housing and located at the upper end of said housing,

flotation means in said housing;

an electrically powered driving circuit for said transducer and an electrical power source for said circuit positioned in said anchor,

said flotation means comprising a single hollow sphere of inorganic nonmetallic material,

said housing including a pair of generally hemispherical plastic members surrounding said sphere, said members including flanges and fastening means for fastening said hemispheres together and for supporting said transducer,

and cabling means for attaching said housing to said anchor including a corrodible wire member retaining said cabling means in coiled configuration.

2. An instrument assembly as set forth in claim 1 wherein said cabling means includes a polypropylene rope and an electrical cable connecting-said driving circuit to said transducer,

said assembly being stored and deployed with said cable and said rope coiled and secured together, said securing means including a corrodible wire link.

3. An instrument assembly as set forth in claim 2 wherein said link is of magnesium which corrodes upon contact with sea water for a period of time, thus permitting the buoyant force of said flotation means to uncoil said cable and said rope.

4. An instrument assembly as set forth in claim 1 wherein said sphere is of glass at least 15 inches in diameter.

5. An instrument assembly as set forth in claim 3 wherein at least one acceleration member of material dissimilar to that of said link is fastened to said link. 

1. An instrumentation assembly for mooring on the bottom of a body of water including a housing, an anchor tethered to the portion of said housing normally positioned nearest said bottom, a sonar transducer fastened to said housing and located at the upper end of said housing, flotation means in said housing; an electrically powered driving circuit for said transducer and an electrical power source for said circuit positioned in said anchor, said flotation means comprising a single hollow sphere of inorganic nonmetallic material, said housing including a pair of generally hemispherical plastic members surrounding said sphere, said members including flanges and fastening means for fastening said hemispheres together and for supporting said transducer, and cabling means for attaching said housing to said anchor including a corrodible wire member retaining said cabling means in coiled configuration.
 2. An instrument assembly as set forth in claim 1 wherein said cabling means includes a polypropylene rope and an electrical cable connecting said driving circuit to said transducer, said assembly being stored and deployed with said cable and said rope coiled and secured together, said securing means including a corrodible wire link.
 3. An instrument assembly as set forth in claim 2 wherein said link is of magnesium which corrodes upon contact with sea water for a period of time, thus permitting the buoyant force of said flotation means to uncoil said cable and said rope.
 4. An instrument assembly as set forth in claim 1 wherein said sphere is of glass at least 15 inches in diameter.
 5. An instrument assembly as set forth in claim 3 wherein at least one acceleration member of material dissimilar to that of said link is fastened to said link. 